1. Field of the Invention
The invention concerns a circuit for generating a sampling pulse raster having a pulse repetition frequency proportional to the variable period of sampled quasiperiodic events.
2. Description of the Prior Art
For analyzing the waveform of a periodic event it is useful if a normalized pulse raster is overlaid on the period of the electrical signal representing the process. This raster divides the curve into sections which can then be sampled and analyzed. In the German Offenlegungsschrift 2,040,913, for instance, an arrangement is described by which the wave shape of the ignition voltage curve of an internal-combustion engine is ascertained by samples taken at definite points in time. In order to do this, several measuring channels assigned to a respective section of the ignition voltage curve are opened at definite points in time, which are predetermined by the underlying time raster, for receiving and possibly evaluating the characteristic signals contained in the ignition voltage curve. The opening is accomplished by means of a control unit which is equipped with time steps built up by a sequence of monostable multivibrators. By means of this prior art arrangement, a fixed time raster is therefore overlaid on the process to be examined. This method is therefore applicable only if the period of the events to be examined is constant. In the case of an ignition voltage analyzer, this would mean that the internal-combustion engine can be examined only at a constant speed. Such a limitation, however, often does not do justice to the requirements of practical operation.
It is an object of the invention to provide a circuit for generating a sampling pulse raster wherein its repetition frequency is proportional to the variable period of quasiperiodic processes.